Many types of fuel filters (also known as “separators” ) are known in the art. A popular type of filter construction is a type that has a filter head to which a replaceable “spin-on” element is attached. The head is a permanent part of the fuel system of the vehicle and includes inlet and outlet connections to the fuel lines. The filter element includes threads on an upper tap plate or cap which cooperate with threads on the underside of the head and allow the element to be spun onto the filter head. The element can be easily removed from the filter head and a new element attached without removing the filter head from the fuel line connections.
One issue with filter elements is that elements with different efficiencies, applications, and/or qualities can sometimes fit on the same filter head. Periodic replacement of the element is necessary such that the filter element will not become so loaded with impurities that fuel flow is restricted. Replacing the element also ensures that impurities are removed from the fuel before it is delivered to downstream components such as fuel injection pumps and fuel injectors, where such contaminants may cause damage. It is important to replace a spent element with the same type of element or one that at least meets the same filtration specifications. It is also important to run the filter with an element installed. Using the wrong type of element or failing to use any element can allow damage to occur to the downstream engine components. Certain elements have been designed whereby the element can only fit a certain filter head, and where the filter will not operate without such a filter element installed, such as shown and described in Clausen, U.S. Pat. No. 5,643,446. In the Clausen patent, a projection supported at one end of the element is configured to engage a valve in the filter head—thereby opening a fuel flow path through the element and head when the filter element is properly installed.
Jensen, U.S. Pat. No. 6,328,883 similarly shows a projection configured to actuate a valve in the filter head; and in addition, among other things, shows and describes a series of holes formed radially through a flange portion of the upper end cap to direct fuel flow into the element. In both Clausen and Jensen the media assembly is assembled through the open end of a cup-shaped canister, and the open end is then formed, such as by roll-forming, over an upper end cap to secure the media components within the housing.
The Clausen and Jensen elements are each relatively simple and straightforward to manufacture and assemble, and address some of the issues identified above; namely, attaching an appropriate filter element to a filter head. Nevertheless these elements provide only a single type of media to remove particles from the fluid stream passing through the element. With more advanced system requirements, it is desirable that such elements also remove all or substantially all of the water in the fuel as the fuel passes through the filter element. Water can adversely effect fuel injectors and other critical downstream components in the engine, and thereby degrade performance.
It is of course known to provide hydrophobic (water-separating) media in filter elements to separate water from a fluid stream; however it is believed such elements have basically just incorporated a single or multi-layered structure into a ring shape, and attached conventional single-piece annular or circular end caps at either end of the media ring. The water collecting on the outside surface of the element drips down into a lower collection chamber or bowl where it is periodically removed.
A more efficient (effective) structure is also know using concentric media rings, with an outer particle-separating media surrounding an inner hydrophobic media, and an annular gap provided therebetween. Water collects on the surfaces of the media rings and can drain down into the lower collection chamber or bowl. The outer media can be optimized for its particle separation capabilities, while the inner media can be optimized for its water separating capabilities. Nevertheless, again it is believed such design has used a single-piece upper end cap -with both media rings being adhesively bonded to the inner/lower surface of such end cap. While this may minimize the part-count of the media assembly, the rigid multi-ring media structure can be misaligned or cock within the housing during manufacture and/or assembly, and otherwise not sit properly in the housing when the open end of the housing is formed over the upper end cap of the media assembly. A misaligned upper end cap can allow leakage from the housing, and also prevent proper sealing between the element and filter head.
It can also be complicated and difficult to properly attach both the inner and outer media rings to the underside of the one end cap. For example, an oven-cured adhesive may be used to attach the end caps. It can be difficult to achieve consistent heat transfer to both media ends for proper curing in a dual-element design; and in some cases the different media configurations and structures can require different curing temperatures, which can be problematic to accomplish with a single, integral structure.
As should be appreciated, the above issues can lead to undesirable manufacturing inconsistencies between elements, and otherwise require time-consuming and complicated manufacturing steps.
As such, it is believed there is a demand in the industry for a further improved filter element that not only prevents improper elements form being installed on a filter head, but which also removes water in the fuel as the fuel passes through the element. And more importantly, it is believed there is a demand in the industry for such a filter element which is simple and straightforward to manufacture and assemble on a consistent and repeatable basis.